Porcelain bushed grinding wheel



n July 13, 1943. J, F. HSCHER 2,324,377

PORCELAIN BUSHED GRINDING WHEEL Filed July 23, 1942 f@ r @HW-@f Patented July 13, 1943 UNITEDl STATES PATENT OFFICE 2,3z4,377 PORCELAIN BUsHEn GRINDING WHEEL John F. Fischer, Drexel Hill, Pa., assigner tov Abrasive Company, Philadelphia, Pa., a corporation of'Pennsylvania 7 Appueation July 23, 1942, serial No. 452,041

5 Claims.

Commercial vitrified grinding implements are l composed of a suitable granular abrasive s ubstance, such as aluminum oxide, silicon carbide etc., bonded with a ceramic material having high vitrifying characteristics. The mixed bond and granular abrasive material is molded into appropriate shapes, which are subsequently subjected to a high vitrifying temperature, i. e. temperatures ofv approximately-2300 F., for eiecting integration of the components, by fusing; vwhile integration of the componentsI of the implements of the resinoid type, for example, is eiected at relatively low temperaturesl i. e. temperatures approximating 360 F.

In the case of implements of smaller sizes, and particularly those of the vitried type, each of the grinding implements is provided with a spindle or mandrel which is rigidly secured therein, and by which the grinding implement is mounted in the-ehuck of a stationary or portable grinding apparatus for operation. These spindles are usually knurled adjacent one end, and the knurled end is inserted and firmly cemented in a preformed axial cavity in the implement.

Under the present practice, the spindles are discarded, with the implements, when the implements are on longereusable.

The spindles are usually formed 'of high grade steel or steel alloy, which, in view of the present emergency, is extremely diiiicult to obtain, thus conservation thereof becomes of paramount importance.

In order to conserve the steel, the present invention is directed to the provision of vitrified abrasive grinding implements having interchangeable spindles, whereby a single spindle may be employed with'an iniinite number of different implements in succession.

It has been known in the art, heretofore, to provide abrasive wheels of the resinoid and other bushings, with plain or threaded bores, `in the molds in which the implements are shaped; and to mold the implements around the bushings before subjecting the molded articles to low firing temperatures required for effecting integration of the components thereof. This procedure is made possible by reason of the integrating tempera- Ature of the bonding material of the implement being lower than the fusing or scaling temperatures of the metal of which the bushings are composed.

It has also been known to provide threaded spindles for interchangeable mounting in the threaded bores of. the metal bushings, in the low temperature integrating \`types ofimple-- ments.

It has also been known to form axial cavities in other types of molded abrasive wheels and, thereafter, to fill such cavities with mo-lten Babbitt metal, and to form plain bores in the metal plug during pouring thereof, or to drill and tap the plugs after solidication to receive threaded spindles.

Due to the extremely high integrating temperature of the vitried implements, it is impractical. to mold metal bushings therein, as vthev metal.

obviously would scale or fuse to such an extent as to render the bushings Within the Wheels etc.

' useless.

The filling of preformed cavities with babbitt metal for drilling and tapping to receive interchangeable spindles is unsatisfactory in most instances, due to the softness of the metal permitting the spindles to become loose in the wheels etc. in operation.

In accordance with the present invention, a satisfactory interchangeable spindle structure for vitried abrasive grinding wheels etc. is made possible by the use of bushings which are composed of high grade ceramic material having la higher fusing temperature than the bonding material of the vitrified grinding implements. Preflow temperature integrating types with interchangeable spindles. However, prior to the present invention, no satisfactory substitute for the integral spindle 'in the vitrifled jtype of abrasive grinding wheel, point etc. has been evolved.

In the low temperature integratingv types of implements, it hasbeen known to place metal erably, these bushings are composed of a ne grain porcelain, as will be morefully disclosed hereinafter, reference being had to the accom- 'panying drawing of which:

Fig. 1 is a longitudinal sectional view of a vitrifled'abrasive grinding implement in the form. of a Wheel or point provided with an internally threaded porcelain bushing and an interchangeable spindle, in. accordance with the principles` A of the present invention;

Fig. 2 is aI detached perspective view of the porcelain bushing shownin Fig. 1;

Fig. 3 vis afiongitudinal sectional view of the above.

In accordance with the present invention, the p porcelain bushings 3 of Fig. 2 are preferably composed of a fine grain porcelain of the steatite or similar type vitreous body of the better grade, such, for example, as are used in the manufacture of spark plugs for internal combustion engines etc. f4

v The porcelain bushings 3, in accordance with the usual practice followed in the manufacture of spark plug porcelains and similarly high grade porcelainware, are preferably provided with a high gloss on the exterior surface thereof, which is produced by dipping or otherwise coating the articles, prior to final firing thereof, with a suitable glazing, after which porcelainware is usually fired at temperatures of approximately 2500 F.v

A practical type of 'glazing substance which is adapted for use on the bushings 3, for the purpose of the present invention, is one which is generally known as an empirical formula, as follows:

Ko 0.30 Co {No} A1203 and of which the following batch weights are given as a practical example:

0.50 (SiO2 5.00

Parts by weight Potash feldspar 167 Whiting 70 Kaolin 52 Flint 108 corresponding to the exterior shape of the body I of the wheel or point, after which the green f unflred mixture of granular abrasive material and ceramic-bond material, such as hereinbefore described, is compressed within the mold, around the insert 3, with the interior surface 2 of the compacted mixture in firm contact with the glazed exterior surface 4 of the insert 3.

After the green molded wheel I and preflnished insert 3 are assembled, and -removed from the mold as illustrated in Fig. 3, the assemblage Is placed in a suitable oven or kiln and fired at temperatures of approximately 2300 F., as noted In the course of this firing, a fusion between the outer glaze l on the preiinished porcelain insert 3 and the bonding agent forming and lying adjacent the surface 2 of that portion of the green wheel I immediately surrounding the insert 3 is effected, as indicated at 4a in'Fig. 1. This fusion causes the porcelain bushing I to become an inseparable integral part of the wheel I, whereby relative movement, either circularly or. axially, between `the bushing and the Wheel is thereafter absolutely prevented.

During the course of manufacture of the porcelain bushings 3, each bushing is provided with an axial bore 5, which may be plain or provided with internal threads 6, as desired, the threads 8. under such circumstances, being formed during the molding of the bushings while the bushings are in their green prefired state.

As shown in Figs. 1 and 3, during the assembling of the finished bushings 3 and the green wheels I in the molds, the end surface 'I of the bushing 3 is aligned iiush with the end surface 8 of the green wheel I, and this relationship is maintained throughout the firing operation and until integration of the components of the wheel and simultaneous fusing thereof with the bushing 3 has been accomplished.

In accordance with the present invention, the threads 6 in the axial bore 5 of the lbushing 3 are adapted to receive screw threads 9 which are formed on a spindle I0, along one end II thereof. The opposite end I2 of the spindle I0, in the present instance, is of plain circularform adapted for use in ordinary spindle-holding chucks. dles I0 may be squared, tapered, or of any other desired cross-sectional or longitudinal shape without departing from the spirit of the invention.

Intermediate the threaded end I I and the plain end I2 of the spindle I0, each spindle is provided with an annular flange or collar I3 which preferably is formed as an integral part of the spindle. The shoulder I4 of the flange I3 is adapted to abut firmly against the fiat face 1 of the bushing 3.

It will be noted that the vthreaded endII, of the spindle I0, beyond the face I4 of the flange I3: is shorter than the depth of the axial boring 5 of the bushing 3, whereby it would be impossible to thread the spindle into the boring 5 until the extreme end I5 of the spindle made contact with the base surface I6' of the bore 5, which, if subsequent relative rotation between the threaded spindle and the threaded bushing were effected, might cause the porcelain threads 6 to be stripped or broken by the metal threads on the end I I of the steel spindle I0.

The jamming of the face I0 of the spindle flange against the face 'I of the bushing affords a rigid but readily detachable connection between the wheel and the interchangeable spindle, I Il.

While the inner ends'of the bushings 3 have been shown as semispherical in Figs. 1, 2 and 3, and the body of the bushing has been shown as purely cylindrical, it will be understood that the inner ends of the inserts may be flatand open, as shown in Figs. 4 and 5, or fiat and closed, as shown in Figs. 6, 7 and 8 or As illustrated in Figs. 4 and 5, the bushings 3c are open at both ends and provided in the axial bores thereof with screw threads 6c extending from end to end thereof or to a lesser extent if desired.

As illustrated in Figs. 6, '7 and 8, the closed ends 20, of the bushings 3a and 3b respectively, may be provided with transverse grooves, as indicated at I8 in Fig. 6, or transverse ribs'as indicated at I3 in Figs. 7 and 8, while the bodies of the bushings may be cylindrical, rectangular or polygonal, .if desired, without departing from the spirit of the invention, deviation from the cylindrical formor the spherical inner end beingprovided, in some instances if desired, to assure against relative circular movement between the prered bushing and the green body of the wheel whilek being removed from the molds and while being placed in the kiln. Such relative movement may impair the otherwise snug fit between the outer glazed surface I of the bushing 3 and the surface 2 of the green material of the implement before fusion therebetween is effected.

However, the outer ends I2 of the spinany other desired The bushings 3a, 3b and 3c of Figs. 5, 6, 7 and 8 are adaptable for use in the wheel or point type of implement, as shown in Fig. 1, to receive the threaded end of the interchangeable spindle l0, or these bushings may also be used in the disc type of vitried implementy lc, shown in Fig. 4, for securing a backing plate 25 to the disc, in which case a series of the inserts 3c are placed in and integrated with the body Ic of the disc at a number of relatively spaced points, about the axis of the disc, to receive the threaded ends llc of suitable bolts Ic by which the backing plate 25 of metal or other suitable material -is secured to one side of the grinding disc.

It will be understood that the inserts of the present invention are preferably of ordinary composition as employed in the manufacture of porcelainware of the commercial varieties of the better grades, i. e. those using a fine grain base, such as talc, and any of the usual commercially employed glazings, which are susceptible to fusion with the vitreous bonding agent of the abrasive grinding implements. The composition'of the implements likewise is preferably the same as commercially used in the art, no special ingredient being required in either the composition of the implements. the composition of the insert. or the composition of the glaze employed on the bushing -in order to practice the present invention successfully.

I claim:

1. A vltrifled abrasive grinding implement, an a prefired ceramic-insert embedded therein prior to firing of said implement and fused therewith by subsequent ring of said implement.

2. A vitrified abrasive grinding implement formed of granular abrasive material and a bonding material of relatively high fusing temperature, a preiired ceramic insert having a relatively higher fusing temperature embedded in said implement and an intermediate fiuxing 'substance having a fusing temperature less than said bonding material for uniting said insert and said implernent.

3. A/'vitried abrasive grinding implement' formed of granular abrasive material bonded with a bonding material of relatively high fusing temperature, a ceramic insert including a bonding material of relatively higher fusing temperature embedded in said implement, and aglazing material on the embedded surfaces of said insert and fusible at a temperature consistent with the fusing temperature of the bond of said implement for fusing said insert with said implement as an inseparable integral part thereof.

4. A vitried abrasive grinding implement and a prered porcelain bushing embedded therein prior to ring of said implement and fused therewith by subsequent firing of said implement.

5. A vitried abrasive grinding implement and a prefused externally glazed porcelain bushing embedded therein prior to ring of said implement and fused therewith through said glaze by subsequent ring of said implement.

' JOHN F. FISCHER. 

